Brian Paddick: Truth, lies and happy pills

The first openly gay senior policeman, aka the 'Cannabis Cop', here reveals that after the shooting of Jean Charles de Menezes, he suffered severe depression. Now the Lib Dem is in the final straight of the race to be Mayor of London

Laughing ex-policeman and London mayoral candidate Brian Paddick outside the Lib Dem headquarters inCowley Street, London (Abbie Trayler-Smith)

Brian Paddick is beautifully turned out, as ever: Gucci suit and tie, silver hair cropped and quiffed. He speaks carefully, as if giving evidence in court. So it feels all the more remarkable that he is talking about falling apart. "I became severely depressed as a consequence of the way I was treated," the London mayoral candidate says of his reaction to a row with Sir Ian Blair, his old boss at the Metropolitan Police. "I got myself into a pretty bad way... with appropriate medical support." What does that mean? Anti-depressants? "The works." Prozac? "It wasn't Prozac," he says, "but whatever the modern equivalent is."

Before the shooting of Jean Charles de Menezes, Paddick was best known for being the highest-ranking openly gay cop in the country, and for his relaxed attitude to cannabis. But after the innocent Brazilian was killed by police officers in 2005, there was an inquiry – and Paddick, an assistant deputy commissioner, gave evidence that contradicted statements by Sir Ian about just how soon the head of the Met knew his officers had made a deadly mistake.

"I couldn't get my head round how I was the one who had been completely open and honest about what had happened after the shooting, [yet] I was the one who had been sidelined," says Brian Paddick. Now the Liberal Democrat candidate for mayor, he ought to be laying out his plans for the capital city. Instead, in a basement restaurant in Westminster, he is talking about suffering from severe depression.

His rivals, Ken Livingstone and Boris Johnson, may be larger than life, but it is hard to imagine them being quite so confessional. This is an election, and there is every reason to suspect Paddick and his advisers have decided it is time to appear a little less buttoned-up and a little more vulnerable, but still, candidates don't usually speak like this.

His condition worsened when he was sidelined into an administrative job after the inquiry, he says. "And there was Ian Blair carrying on as if nothing had ever happened."

The force was found guilty of catastrophic errors, but the commissioner remained in place. "I couldn't come to terms with it, initially. During a session, my counsellor said to me: 'It looks to me like you have got two possible alternatives: shoot Ian Blair or throw yourself in the river.' She's an interesting counsellor."

Sounds like it. So how did he get through it all? "I decided there must be a third way," he says, smiling grimly at his own sort-of-joke in using the New Labour phrase. "The counsellor and I talked about the possibility of me meeting Ian Blair and saying to him: 'Look, you know the truth and I know the truth, because we were both in the room at the same time. The fact is, I'm only a DAC, and that's why I've been sidelined and you're carrying on as commissioner. But I'm the one who can sleep at night, and you need to know that.'

"I never did go and see him and tell him that, but having rationalised that in my own mind helped me get over the problem. That and British Airways."

After taking strong medication for three months, he lost the lot when his luggage was mislaid at Heathrow. "I didn't see it again for another two weeks." He understands the suffering of Londoners at T5, then. But it did him good. "Both my partner and I had time off; he was around and I wasn't feeling too bad. Instead of taking the drugs again when the bags turned up, I went to see the doctor, and he said: 'I don't think you need them any more.' So British Airways saved me."

He smiles again, but it's not funny. "When you have an illness like that, it's just extraordinary what ridiculous things you believe," he says. "I believed I had no ability, no skills, I couldn't possibly leave the police, because nobody would believe me. And here we are, running for mayor."

On the day we meet, the polls place Boris and Ken on 42 per cent each, and Brian – although that seems far too informal for the straight-backed man dissecting a mango crème brûlée – receives just 10 per cent of the potential vote. He can't win, can he? Ken would splutter at that, Boris would bumble, but Brian states flatly, as if reading from an incident book: "That is clearly a perception that we need to demolish."

He honestly believes his popularity will be heading in a northerly direction as more people hear and see him on the hustings and recognise "the safe pair of hands in this election. The reputation I have earned over years in the police service is as a man of integrity ... someone who is prepared to be honest about himself and [his] sexuality."

Let's see how honest he is, then. The first question is inevitable, given his party leader's statements. Nick Clegg was asked by GQ magazine how many people he had slept with, and said it was "not as many as 30". So, Brian Paddick, how many people have you slept with? "A lot less women than Nick Clegg," he says quickly.

Paddick knew he was gay as a child in south London, but was married for five years in the Eighties. "It was a genuine attempt to live as a straight man," he says. "It's what my faith as a Christian expected of me. It's what my parents expected of me. It's what the police service expected of me. Mary was a very beautiful and charming woman. It was a genuine attempt to try and deny my sexuality and to 'do the right thing'.

"Five years is a good try. But during that period it became increasingly apparent that I was never going to be at ease with myself unless I was honest about my sexuality. It was a case of breaking it to her gently."

This he did in a Chinese restaurant. "She was upset. We still loved each other. But when we got home she said: 'If you told me you were leaving me for another woman I would never have forgiven you. But I realise that in you having a relationship with another man there is something I could never give you.'"

Tempted for a moment to make a joke, he thinks better of it. Are they still in touch? "Yeah. She phoned me a couple of years ago to say she had finally become a mother, which is great." He showed her relevant passages from his autobiography before it was published this month. "We're still on very good terms."

The Clegg question has still not entirely been answered though. So how many men has he slept with? "Mind your own business." Four male partners are mentioned in his book, one of whom sold a story "full of lies and distortions" to a tabloid. Since Paddick decided to run for mayor, there has been intense interest in the man he is sleeping with now. How do they deal with that? "We go to things together. If there are snappers there, then we are unable to talk to each other. Everyone is desperate to get a picture of us together."

Is that honest? "What? I'm not ... His name's Petter, he's a civil engineer from Norway, we're in a long-term relationship. We met in Ibiza, in a bar. What is there [I'm] not being honest about? But if you run for mayor, you give up your right to privacy. If Petter wants to give up his right to privacy, that's a matter for him and not for me. At the moment, he doesn't want to."

Other friends are rather less publicity shy. Sir Elton John and his partner, David Furnish, for example, support his campaign. "I met David first, then there was this party to celebrate the 10th anniversary of Attitude magazine. Elton comes up to me and says: 'Hello, Brian. I'm a big fan of yours.' Which is just bizarre. I had already been talking to Cilla, and been introduced to Lulu, then Elton. David had heard this great group he wanted Elton to hear, so they were performing. They were called Scissor Sisters. I was sitting back to back with somebody. I said to David: 'We haven't been introduced.' It was George Michael. But it does get annoying: every time I see George Michael he says: 'Have you got a spliff?'"

Dizzying stuff. George's joke is a reference, of course, to the time when Brian Paddick first hit the headlines, in 2001, as police commander for Lambeth. He tried a pilot scheme, ordering officers to warn and not arrest people with marijuana, and the tabloids have called him Cannabis Cop ever since. But it has to be said that his style won him the backing of the black newspaper The Voice, and many residents of Lambeth. It's not surprising that his No 1 policy pledge as mayor is to bring down crime rates. He would take over the Metropolitan Police Authority and (presumably after getting rid of Ian Blair) tell officers: "Try to re-establish yourselves as citizens in uniform, people who are actually on the same side as the public, because they don't think that now."

If Paddick does come third on 1 May, as expected, he could still be the election's kingmaker by advising his supporters who to back with their second-choice votes. Who will it be? He's not saying. But there may be a very big clue in his revelation that the Conservatives actually asked this Lib Dem member to stand for them before Boris. They offered impressive support in people and money, but he said no. "My mum said: 'Churchill did it. He crossed the floor. But your grandmother never forgave him for it.'" Paddick wears his grandmother's wedding ring. "I just couldn't, even though that might have given me the better chance. Unfortunately for me, I'm a man of principle."

The bigger question, of course, is why anyone outside the capital should care? This appears to stump him for a moment or two, before he says: "LGBT – lesbian, gay, bisexual and transgender – people outside London are very interested to see how the first openly gay person running for a very high profile office gets on. More generally, people want to see how two parties with new leaders are going to do in their first major test, potentially so close to a general election."

Still awake, Newcastle? Then imagine his heavyweight rivals puffing their way over the cobbles in the London Marathon this morning, as Brian Paddick is due to be. He's fit for office in that sense, anyway. He'll be wearing a T-shirt that says Running for London Mayor. That's one of his better jokes, actually, but so what, if the other two are better at making people laugh?

Unlikely as it might have seemed in the past, in the Boris and Ken Show, Brian Paddick is happy to play the straight man.